California · For landlords and property managers
California Mold Disclosure Rules for Landlords
Under Health and Safety Code 26147, part of California’s Toxic Mold Protection Act, a landlord who knows of mold that exceeds permissible limits or poses a health threat must disclose it to tenants in writing. The state never adopted numeric limits, so most owners treat known, unremediated mold as something to disclose.
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The law
Do landlords have to disclose mold in California?
Yes, in some cases. Health and Safety Code 26147 requires landlords to give written disclosure when they know mold is present that exceeds permissible exposure limits or poses a health threat. The duty turns on what the owner knows, so a tenant report, an inspection result or a lab report can all trigger it.
Section 26147 sits inside the Toxic Mold Protection Act, Health and Safety Code 26100 to 26156. California never adopted numeric exposure limits for indoor mold, which is the main reason the disclosure rule is harder to apply than it sounds.
The gray area
What does “exceeds permissible limits” mean if California has no limits?
There is no state number to test against. No spore count or lab result tells you, by law, that disclosure is or isn’t required. That leaves the “health threat” part of the rule and the owner’s own knowledge as the practical tests, and it is why careful owners lean toward disclosure.
A lab report can still help. Air samples compared with an outdoor control show whether indoor levels are elevated, and surface samples show what is growing. But a “normal” result doesn’t settle the legal question, and neither does an elevated one. Visible growth is also a separate issue: since SB 655, visible mold can be a substandard-housing condition under Health and Safety Code 17920.3, whatever a lab says.
| Rule | What triggers it | What it requires |
|---|---|---|
| HSC 26147 (disclosure) | Owner knows of mold that exceeds limits or threatens health | Written disclosure to tenants |
| HSC 17920.3 (SB 655) | Visible mold growth, except minor mold on surfaces that normally get wet | Correction as a substandard condition |
| Civil Code 1941 and 1941.1 | Any condition that makes a rental uninhabitable | Repair to keep the unit habitable |
Plain-English summary. Disclosure does not replace the duty to fix the problem.
In practice
When do landlords usually give a mold disclosure?
Most often at three points: when a new tenant is about to move into a unit with known, unresolved mold; when mold is found in an occupied unit or building; and when remediation work is scheduled. The common thread is knowledge. Once you know, the safest course is to put it in writing.
- Before a new lease: if mold is known and not yet remediated in the unit being rented.
- After a finding: when an inspection, a lab report or a code inspector confirms mold in an occupied unit.
- Before work starts: tenants need written notice of entry and work dates anyway, following California’s entry notice rules.
- Shared problems: when the source, such as a plumbing stack or roof, affects more than one unit.
What owners commonly include
The statute requires the disclosure to be in writing. Beyond that, ask your attorney about form and wording. Many owners include the facts a tenant would want: where the mold is, what caused it, what testing found, what will be done and when, and who to contact. Have your attorney review any template before you use it.
Records
What records support a mold disclosure?
A disclosure is only as good as the facts behind it. An inspection report, moisture readings and, where useful, lab results from an accredited lab tell you what to disclose. A clearance report after remediation shows when the problem was resolved.
- Inspect. A visual inspection with moisture mapping finds the extent and the source. See apartment mold testing for when lab samples add value.
- Disclose in writing. Give the tenant the facts, and keep a copy with the delivery date.
- Remediate. Fix the moisture source and remove growth under containment following IICRC S520. Our page on mold remediation in apartment buildings covers occupied units.
- Verify. Independent clearance testing documents the result. Give the tenant a written update once the work passes.
If a code inspector is already involved, the same records serve both purposes. Our guide to responding to an LAHD or County mold citation lists what to keep.
What about selling a building?
Disclosure to buyers in a sale is a separate set of rules from the tenant disclosure in Section 26147. Ask your agent and attorney what applies. Buyers and sellers often order a real estate mold inspection during escrow so both sides work from the same report.
FAQ
Mold disclosure questions from California landlords
Do landlords have to disclose mold in California?
Under Health and Safety Code 26147, a landlord who knows of mold that exceeds permissible limits or poses a health threat must disclose it to tenants in writing.
What is the Toxic Mold Protection Act?
It is a California law in Health and Safety Code 26100 to 26156. It deals with indoor mold and includes the landlord disclosure rule in Section 26147. California never adopted numeric exposure limits under it.
Is there a legal mold level that requires disclosure?
No. California never adopted numeric mold exposure limits, so no spore count settles the question. The practical tests are what the owner knows and whether the mold poses a health threat.
Does disclosing mold mean I don’t have to fix it?
No. Owners must keep rentals habitable under Civil Code 1941 and 1941.1, and visible mold can be a substandard condition under Health and Safety Code 17920.3.
Do I need a mold test before I disclose?
Not necessarily. The duty turns on knowledge, and visible mold is knowledge. Testing helps when growth is hidden or you need to know what is growing and how far it extends.
Is mold disclosure to a buyer the same as to a tenant?
No. Sale disclosures are a separate set of rules from the tenant disclosure in Section 26147. Ask your agent and attorney what applies to your sale.
This page is general information, not legal advice. Talk to a landlord-tenant attorney or your local apartment owners’ association about your building. For the full picture, return to our mold compliance hub for property managers or read our plain-English guide to California mold laws.
Sources
- California Health and Safety Code 26100–26156 (Toxic Mold Protection Act), including 26147
- California Health and Safety Code 17920.3 (SB 655); Civil Code 1941 and 1941.1
- US EPA, mold guidance: epa.gov/mold
- ANSI/IICRC S520, Standard for Professional Mold Remediation
Last updated November 2026.
Need to know what you’re disclosing?
We inspect, find the moisture source, and give you a written report and a written quote before any work starts. Call (213) 659-0672, 24/7 across Los Angeles County.